Also known as "decimal logarithms". logarithms based on 10 is expressed by the sign lg. For example, lgA indicates A logarithms with base 10, where A is a true number. Any positive number use logarithms can be expressed as the sum of one integer number and one positive small number (or zero). The whole number part is called logarithms "first number", and the positive pure small number (or zero) is called logarithms "last number". use logarithms There is a logarithms table.

use the number method of scientists to express one positive number as a formality that contains an integer small number and the power product of 10's integer number, and then take use logarithms

Example: lg200=lg(10^2*2)=lg10^2+lg2=2+0.3010

lg20=lg(10^1*2)=lg10^1+lg2=1+0.3010